The present invention involves a head-stabilized method and apparatus designed for the diagnosis and treatment of vestibular disorders involving symptoms of dizziness, vertigo and/or imbalance. It also relates to the structures of certain special devices that are particularly suited for use with this method and apparatus, and to certain procedural approaches that the structure and method of the invention make advantageous.
In a manner of speaking, the invention recognizes, and centers attention on, the discovered significance of utilizing various, plural-simultaneously-employed sensors/detectors which are specially positionally stabilized, both (a) with respect to the head of a patient, and (b) with respect to each other, for the simultaneous gathering, and immediate computer processing, of plural-parameter data which can lead to accurate diagnoses and treatment of disorders of the types just generally mentioned above. Both mentioned categories of stabilization have been found to be important and unique in this sophisticated and challenging field of medical practice. Positional stabilization, undertaken in accordance with practice of the invention, leads to accurate correlation of different simultaneously gathered data components, and thus leads, in turn, to significant improvements in diagnostic speed and accuracy, and in trustable opportunities to rely with confidence on rapid, computer-based vestibular analyses and conclusions.
Dizziness, including vertigo and imbalance, is one of the most common complaints presenting to the physician. Although these symptoms may be caused by a variety of abnormal conditions affecting either the peripheral or central nervous systems, the cause can most commonly be traced to abnormalities involving the vestibular endorgans in the inner ear, or, less frequently, to their associated neural pathways to and within the brain. The vestibular endorgans are actually mechanico-transducers that normally sense, as information, either angular or linear acceleration of the head. This information is relayed, either through reflex, or after central integration with somatosensory and visual information, to the eyes (vestibular ocular reflex) (VOR) or the muscles of postural control (vestibulo-spinal reflex) (VSR). Thus, diagnosis and treatment of these disorders has been very dependent upon the ability to observe and quantify the reflex output of these systems, or the behavioral response thereto, thus leading to the localization of pathology and treatment directed thereto.
The anatomical sensors of angular acceleration, which provide the percept of rotation in space in any plane, are the semicircular canals which are located with three on each side within the inner ear, oriented orthogonally to each other. Each semicircular canal acts as a sensor of rotation in the plane of its orientation. It contains fluid that, due to its inertia, lags angular accelerations or decelerations of the head in the plane of the canal, and thereby actuates a sensor of fluid displacement, the cupula. This activation provides information via neural pathways to the brain stem, which information is carried via a reflex arc to the eye muscles, called the vestibulo-ocular reflex. During angular movements of the head, this reflex keeps the eyes oriented in space via a counter-rotation until the eyeball reaches a certain point, whereupon there is a quick correction in the opposite direction called a saccade. When such activity is repetitive, what results is an involuntary jerking motion of the eyes, called nystagmus, which occurs in the plane of the semicircular canals that generate it. By observing such nystagmus under various conditions, one can determine whether the semicircular canals are functioning normally and, if not, which canal is dysfunctional. One can also often determine the nature of the dysfunction. Also, the nystagmus behavior can be followed in the course of treatment, thus to monitor effectiveness. Dysfunction of the semicircular canals results mainly in symptoms of vertigo. The cause of dysfunction can be neurological or mechanical.
Quantitative assessment of the VOR and other eye movements under various conditions is carried out in a standard battery of tests known as nystagmography. When eye electrodes are used to detect eye movement, it is called electronystagmography (ENG). When video technology is used to detect eye movement, it is called videonystagmography (VNG). Testing is usually carried out in a light-obscuring environment in order to minimize the effects of optic fixation on the suppression of nystagmus. To varying degrees, nystagmus can also be suppressed by lack of alertness, by certain drugs, and by and habituation.
The standard ENG/VNG test battery includes a few standard head positions that are intended to provide an analysis of positional vertigo. However, these standardized test positions do not employ the ideal anatomical positions for obtaining useful information. Thus, new methods of investigating the causes of positional nystagmus and vertigo call for new standard positions for screening purposes, plus the triggering of more definitive tests when indicated. In addition, nystagmus data is typically acquired and analyzed in small segments which completely ignore nystagmus occurring during intervening periods and transition moves. Inasmuch as nystagmus occurring in a particular test position will be dependent upon numerous factors, such as (a) the rapidity and method of the just-mentioned maneuver, (b) the time lapse after a test position is reached until the data-acquisition run is commenced, and (c) the exact angles of the test positions, etc, the usual ENG/VNG test battery, as now generally carried out, is not optimally effective and accurate.
What is needed, and is definitively provided, among other things, by the present invention, is a method of carrying out the indicated screening and selected tests that can be automated and programmed to carry out certain screening tests and, but that is (a) capable of interjecting certain more definitive tests when so indicated by the screening tests, (b) can perform tests that are physiologically more meaningful than those previously done, and useful in diagnosing and treating a subject, (c) can acquire real-time data in a continuum throughout a test session, (d) can distinguish between normal and abnormal nystagmus, and (e) can, through careful programming, accomplish these tasks in as short a time as possible. Means must also be available that selects, analyzes and displays acquired data in a brief, understandable, and reliable summary.
The anatomical sensors of linear acceleration, the otolithic organs called the utricle and saccule, are located on each side in the inner ear. Each is made up of a layer of heavy particles that is attached to hair cells that can, when stimulated, initiate a neural discharge. When the head is placed in various positions relative to gravity, or moves linearly in various directions, the resulting change in the inertio-gravitational vector acting upon the particles presents changing forces of strain that modulate the neural discharge of the attached hair cells. The resulting neural input leads to the brain stem, thence to the spinal nerves, and finally to the muscles of postural control in the vestibulo-spinal reflex. Simultaneously, at a higher level, there is a subjective sense of the inertio-gravitational vector, called graviception, that in a normal subject is accurate to within a few degrees.
Abnormal conditions adversely affecting the otolithic organs cause mainly symptoms and signs of imbalance. This imbalance of otolithic origin results from either unstable neural input from an otolithic organ, or organs, or a bilateral deficit. Unstable neural input results from otolithic function that is either recently reduced from the normal, or is distorted from the normal input. This distorted neural input usually results from aberrant receptivity of the otolithic organ to non-gravitational forces, such as sound and changing intralabyrinthine pressure. Central compensation generally takes place adequately over time for the reduced form if it is unilateral and becomes stable, but compensation is delayed or not forthcoming in response to the distorted form because of its persistent instability. Thus, the distorted form is by far the more common cause of chronic vertigo. It is seen frequently as the principal mechanism of post-traumatic vertigo.
Research by me and others has indicated that a quantifiable assessment of the distorted neural input arising as a consequence of aberrant receptivity of an otolithic organ can be accomplished by determining the adverse postural effects of either sound or a changing intralabyrinthine pressure, as can be ascertained in a standing subject by observing, directly or by measuring apparatus, an increase in sway or a tendency to fall. This is usually done through posturography with the subject standing on a force plate, but, uniquely with respect to the present invention, as will be seen, is done through gravitational and angular sensors, and an inclinometer (or inclinometers), which are appropriately stabilized on the head and with respect to one another.
A problem with analyzing adverse postural effects for this purpose is that test subjects are usually acutely aware of their recent postural misperceptions that have resulted in abnormal sway or fall in a particular direction, and can quickly compensate for these misperceptions to some degree when presented with the same apparent stimulus. Thus, if air pressure that is presented to an ear canal of a standing subject with eyes closed were to cause a sway, or a fall, in a particular direction, the next time the same stimulus is presented, that same subject will habitually tend to compensate by counteracting the sway or fall. This is because, on the first trial, the subject received somatosensory feedback from the feet and postural muscles indicating that involuntary sway, or a fall, in a particular direction, took place. This tendency to compensate results in limited repeatability, and thus, questionable reliability of such a test using postural control as a measure. This issue is addressed by the present invention largely in the form of presenting sound and pressure stimuli in an alternating, variable and random, computer-controlled fashion, rather than by presenting stimuli to one ear at a time, and in a predetermined manner. This novel method results in greater repeatability and reliability, and is discussed further below.
Many subjects with vertigo symptoms complain of aggravation of these symptoms by loud sound, or by conditions that are known to impart pressure change to the intralabyrinthine fluids. Aberrant receptivity of the labyrinth to sound or intralabyrinthine pressure change can occur in either the semicircular canals, thereby adversely impacting the VOR system and producing nystagmus, or in the otolithic organs, thereby adversely impacting the VSR system and producing abnormal postural effects and altered gravitational perception. The latter condition, involving the VSR system, occurs far more frequently, yet the most commonly used procedure in testing of the effect of sound or intralabyrinthine pressure change involves only observation of the eyes. Thus, in the commonly used method of performing Hennebert (pressure) test and Tullio (sound) tests, the subject is seated and the clinician observes the eyes, either directly or with the assistance of magnification or electronic means, for abnormal nystagmus, and thus the postural effect information is seldom sought. Given this, an improved method is needed for quantifying and localizing the effects of sound and intralabyrinthine pressure change on the VSR arc by monitoring their effects on postural control, which is basically a test of gravitational perception, because sound and pressure have been shown in these situations often to cause an altered perception of the inertio-gravitational vector.
In the present state-of-the-art, quantitative information on the status of both the VOR and the VSR requires two separate devices, taking up more space in the vestibular laboratory and adding to expense. In addition, several valuable existing tests have not been utilized significantly outside of research laboratories because of the expense involved in the equipment to perform each test separately. In the practice of the present invention, placement of multiple stimulus and response modalities in conditions stabilized to the head solves these problems.
One example of this is seen with vestibular lithiasis, or benign paroxysmal positional vertigo and different variants, whereby abnormal particles in the semicircular canals render the canals sensitive to linear acceleration, including gravitation, creating symptoms of vertigo in response to position change of the head relative to gravity. These conditions are very common, and can often be improved or corrected by repositioning maneuvers, whereby the particles are moved, via a particular sequential positioning of the subject's head with optional induced head oscillation, to an area of the labyrinth where they no longer produce abnormal responses. Most subjects with these conditions can be treated successfully by canalith repositioning maneuvers, including variations thereof, collectively known as particle repositioning maneuvers, which are designed to cause migration of aberrant particles to an area of the labyrinth where they no longer affect the dynamics of the semicircular canal.
These repositioning maneuvers are typically carried out manually on a table with a high success rate in the less complicated cases. However, for the more complicated cases, optimal performance of these maneuvers requires ongoing, real time observation and analysis of nystagmus. The nystagmus pattern may rapidly change during the performance of maneuvers, sometimes indicating the need for a critical change in strategy in the middle of a maneuvering sequence. In addition, and as mentioned above, the nystagmus patterns that subjects may display in response to maneuvers may be rapidly changing and complex, yet immediate interpretation is often required, and this requirement becomes more acute when the need for a change in strategy is indicated (e.g. a conversion of the causative particles from the posterior to the horizontal canal, or the development of a jamming of the particles). Very challenging, there is the need for the operator, during an entire sequence of maneuvers, to envision the 3-D orientation, with respect to space and gravity, of the semicircular canals inside the head, as well as the apparent position of the particles within those canals. This multi-level observation requirement is quite difficult because of the constant changing orientation in space of the subject during maneuvers. As will be seen, the present invention confidently addresses and solves these problems.
Thus, for optimum positional testing and particle repositioning strategy, the present invention features a head-stabilized 3-D orientation and tracking capability for generating data simultaneously regarding (a) the actual orientation, relative to space and gravity, of the semicircular canals of a subject, as well as (b) the angular acceleration being acutely imparted to the semicircular canals. Information regarding linear acceleration, possibly along with additional information regarding spatial inclination (derived from an appropriately employed inclinometer, or plural inclinometers) may be made available for use in this setting in accordance with the structure and practice of the present invention. Such data, fed to a watchful, and operatively and properly algorithmed computer, is displayed to the operator in a form that projects the actual orientation of the semicircular canals within a subject's head to a graphic user interface (GUI) image of the semicircular canals. This image is presented in a simulated environment that makes the orientation of gravity evident.
One related and very important novel contribution of the present invention is its demonstrable ability, on-the fly, so to speak, to distinguish even very subtly existent pathological (abnormal) from physiological (normal) nystagmus events. This is extremely valuable to the clinician during testing or treatment, because of the fact that the nystagmus being observed in response to head maneuvers often contains components of both pathological and physiologic nystagmus. It is clearly advantageous to be able to observe and analyze just the pathological nystagmus without contamination by physiological nystagmus. Positional stability of sensors and stimulators in accordance with practice of the present invention leads significantly to the reliable ability to accomplish this differentiation.
Physiological nystagmus is mainly induced by angular acceleration of the head, with the slow phase of nystagmatic eye rotation occurring in the same plane as, but in the opposite direction from, head movement. This is a normal response reflex. Thus, by monitoring angular acceleration in addition to linear acceleration, while also monitoring, simultaneously, eye movement, and by doing all of this under conditions wherein the relevant monitoring sensors are firmly positionally stabilized relative both to one another, and to a patient's head, the present invention can effectively distinguish between those components of nystagmus that are physiological and those which are pathological in origin.
Further describing, in relation to this aspect of background information, certain relevant and important characteristics of the present invention, during a system calibration phase, the system of the invention determines the gain of the physiologically evoked nystagmus in each plane and direction. From this, it determines, in near real time, the slow phase component of physiologic nystagmus that would occur with each head movement, and then, during actual testing, removes its contribution to the total computer-generated information readout, thus leaving only the pathological nystagmus in the readout information.
Elaborating a bit on this above, brief summary outline, these pathological and physiological components may occur simultaneously, with each component contributing to the resultant nystagmus, and with the resultant nystagmus thus being made up of the vector sum of the planes, directions and velocities of the simultaneously occurring slow phase components. The slow phase vector for the physiological component is then subtracted from the slow phase vector of the presenting nystagmus, allowing a clinician to view just the purely pathological nystagmus for immediate use in diagnosis and in carrying out repositioning maneuvers. Understanding the investigative importance of performing this vector subtraction, and given the just presented outline describing the relevant data components requiring such subtractive processing, those skilled in the art will be readily equipped to implement an appropriate, computer-based algorithmic approach to accomplishing this.
Practice of the present invention in relation to the field of vestibular disorders, further accommodates the involvement of additional stimuli, such as the modification of air pressure experienced by the ears, oscillation of the skull, electrical stimulation, acoustic stimulation, etc., or any combination thereof, which may create pathologic nystagmus that can be analyzed to assist in the diagnosis and treatment of vestibular disorders.
In general terms, and broadly speaking from one structural point of view, the present invention can be characterized as including an assembly of mechanical, electronic and software components linked to positionally-stabilized, subject-head-worn apparatus, whereby, with a subject (person) oriented in, or moved through, certain positions, that subject may be presented with vestibular-relevant stimuli, such as visual images, sound and pressure change in the ears, head vibration, and therapeutic or diagnostic fluid flow into (and eventually out from) the middle or external ear, and simultaneously observed by both a computer and a human attendant for reflex eye movement, postural responses and spatial orientation as tracked with inertial and other positionally stabilized sensors, and/or by observation of subjective responses. Plural-parameter data, regarding simultaneous positional or other stimuli, and responses thereto, is integrated and analyzed electronically and displayed in an easily understandable form which includes vector analysis (above mentioned) of nystagmus, identification of the originating semicircular canals, and guidance for further tests and treatment. From a methodologic point of view, the invention can be characterized broadly as involving appropriate steps to implement this just-outlined structural view of the invention.
The invention also encompasses the physical characteristics of certain new, head-attachable structures, or devices, which play roles in the delivering of certain ear stimuli relevant to vestibular-disorder diagnoses and treatments, as well as to certain related new procedures.
As will also become apparent, the present invention opens a door to the assembly and use of a very innovative, computer-based, “expert-guided” system. Very specifically it enables the implementation of a feedback-endowed system, wherein a subject wearing device-stabilized (sensors and stimuli deliverers) headgear may be communicatively connected (tethered or “wire-free”) to a computer armed with “expert”-trained algorithm structure which has been “taught” by highly skilled and experienced medical personnel to understand, in a broad spectrum, the significances of observable subject responses to matters such as spatial positions, maneuvers, delivered stimuli, and so on. This computer will be able to react to these observable phenomena with feedback-based information that can do a variety of things, such as (a) inform an attending “medical” operator of the system just what to do next with respect to a diagnostic and/or treatment step to perform with the subject, (b) modify the character, nature, etc., of various stimuli being delivered, or to be delivered, to the subject via the head-worn, device-bearing gear, (c) implement and/or modify the delivery of a liquid substance, such as a treatment and/or stimulation drug, to the subject's ear, or ears, and other things which will come to the minds of those skilled in the art. (One should note that the terms stimulus and stimuli are used herein to refer to all forms of “deliveries” including liquid deliveries for either diagnostic or treatment purposes, to a subject via the stabilized headgear of this invention.).
The invention thus effectively makes possible, anywhere in the world, the functional availability, to subjects suffering from vestibular disorders, of the world's most highly skilled vestibular-disorder experts. By the use of appropriate telemetry, all of this advantage can be invoked via “remote control”. The following summary statements non-exclusively illustrate these “expert-system” possibilities.
Headgear for positional ontological vertigo (diagnosis and treatment) with goggles, inclinometers and accelerometers is employed. A subject is fitted with the headgear of the invention, and is placed on a table lying down. The attending system user (typically a physician) starts a maneuver protocol on the computer, which guides the physician's movements of the subject's head while simultaneously monitoring eye and head movements and analyzing associated pathophysiological nystagmus and head position, for the purposes of diagnosis and treatment assessment and maneuver adjustments where applicable.
Headgear for stimulus-evoked ontological vertigo with goggles, inclinometers, accelerometers, sound, pressure, vibration, light, etc., is employed. A subject is fitted with the headgear of the invention (with ear inserts), and is placed in a chair, or positioned standing up. The attending system user (again typically a physician) starts a stimulus protocol on the computer, which generates a set of ear and/or head stimuli, whose resulting subject eye and head movement responses are simultaneously monitored and analyzed for pathophysiological nystagmus and head position, all for the purposes of diagnosis and additional stimulus-response protocols where applicable.
Headgear for intratympanic drug delivery with goggles, inclinometers, accelerometers and fluid flow system is used. A subject is fitted with the headgear of the invention (with ear catheters), and is placed on a table lying down, or in a chair. The attending system user starts a fluid flow protocol (e.g., drug delivery) on the computer, which provides intratympanic fluid exchange, while simultaneously monitoring subject eye and head movement responses, and analyzing for pathophysiological nystagmus and head position, for the purposes of treatment assessment and fluid flow adjustments where applicable. In this kind of procedure, which should be distinguished from a caloric-stimulus procedure, a local anesthetic such as lidocaine might be employed as a perfusate tag.
These and other features and advantages of the invention will become now more fully apparent as the description which here follows is read in conjunction with the accompanying drawings